Is 5W30 Fully Synthetic Oil?

[VonJoanna]

5W30 engine oil is not entirely fully synthetic, as different grades of oil share this viscosity rating. For example, the 5W30 variants of Mobil Super, Shell HX6, and Castrol GTX are semi-synthetic oils; while Shell HX5, Shell HX3, and Total Quartz 3000's 5W30 are mineral oils. More information about engine oil is as follows: Quality Grade Classification: Engine oils can be categorized into fully synthetic, semi-synthetic, and mineral oils based on quality grades. Fully synthetic oil is the highest quality, followed by semi-synthetic, with mineral oil being the lowest. Standard Four-Season Oil Viscosity Ratings: 5W20, 5W30, 5W40, 5W50, 10W20, 10W30, 10W40, 10W50, 15W20, 15W30, 15W40, 15W50, 20W20, 20W30, 20W40, 20W50. Meaning of "W": It stands for Winter, and the number before the W indicates the oil's fluidity at low temperatures—the smaller the number, the better the fluidity. Conversely, the number after the W refers to the oil's viscosity grade at high temperatures—the larger the number, the higher the viscosity, providing better engine protection.